1. Field of the Invention
The present invention relates to a curved pipe manufacturing method and an apparatus for carrying out the same and, more specifically, to a curved pipe manufacturing method and an apparatus for carrying out the same, in which a straight pipe of a stainless steel or like materias is pressed into a fixed die having a curved cavity of a circular arc to form a curved pipe.
2. Description of the Prior Art
Japanese Pat. Publication No. 54-23677 discloses a curved pipe manufacturing method employing an apparatus as illustrated in FIG. 4, invented by the inventor of the present invention. According to this known curved pipe manufacturing method, a work, namely, a straight pipe 5, is pressed with a presser rod into a curved space conforming to the shape of a curved pipe to be formed, defined by a curved cavity 4 formed in a fixed die 1 so as to extend from the entrance to the exit of the fixed die 1, and a curved mandrel 7 secured to a movable block 6 so as to be inserted into and to be pulled out from the curved cavity 4 and inserted into the curved hole 4 of the fixed die 1, through the entrance of the fixed die 1 to form a curved pipe, then the movable block 6 is turned to pull out the mandrel 7 from the fixed die 1, and then the movable block 6 is turned further to punch out the curved pipe from the fixed die 1 with an ejecting rod 8 attached to the movable block 6 opposite to the mandrel 7.
This known curved pipe manufacturing method, however, has a drawback in that, since the mandrel 7 is seized firmly by the curved pipe, the curved pipe is pulled out with the mandrel 7 instead of being ejected separately with the ejecting rod 8 when the mandrel 7 is pulled out from the fixed die 1 by turning the movable block 6, and hence the curved pipe needs to be removed from the mandrel 7 by some additional means. Accordingly, this known curved pipe manufacturing method is not able to automate the curved pipe manufacturing process.